The present invention relates generally to a service unit for restarting a spinning operation in work stations of an open-end spinning machine after replacement of a yarn cheese with an empty cheese-winding tube, and more particularly to a service unit comprising an auxiliary yarn supply device for providing an auxiliary yarn for restarting the spinning operation after a yarn cheese replacement and a yarn moving device for fixing a new spinning yarn on the new empty cheese-winding tube.
As is known, open-end spinning machines have a plurality of adjacent work stations, each of which comprises a spinning device for manufacturing a yarn and comprises a winding device with a creel and a yarn traversing device for producing a cross-wound bobbin commonly referred to as a cheese.
The work stations of such open-end spinning machines are typically served by automatically operating service units that intervene if a need for service has occurred at one of the work stations. Such a need for service occurs, e.g., in case of a yarn break or if the cheese at one of the work stations has attained its prescribed diameter and must be replaced by a new empty tube.
That is, such service units described, e.g., in German Patent Publication DE 44 43 818 A1 or in DE 43 13 523 A1 not only eliminate yarn breaks but also automatically carry out cheese/empty tube replacements. For example, in the case of a cheese/empty tube replacement, the full cheese is removed from the creel of the particular work station and transferred onto a transport device of the machine. Then, a new, empty tube is placed into the creel, the open-end spinning device started to spin again by means of a so-called auxiliary yarn and the new spinning yarn is fixed on-the freshly replaced empty tube.
The known service units comprise numerous manipulation devices, e.g., a pivotably supported, vacuum-loadable suction nozzle for grasping a trailing yarn wound onto the cheese in the case of a yarn break, and a supply device with a pivotably supported supply tube for making available an auxiliary yarn required after a cheese/empty tube replacement for a spinning restart. Moreover, these service units comprise a yarn placement device for fixing the new spinning yarn on the empty tube and for creating a yarn reserve winding. The new spinning yarn is moved by the yarn moving device into the range of one of the tube plates of the creel in such a manner that a rotating yarn catch device arranged on the tube plate grasps the spinning yarn, draws the yarn into an entrainment groove and fixes the yarn to a greater or lesser extent. Subsequently, a starting reserve winding is prepared by the yarn moving device in the area of the foot of the new tube.
The described service units have proved themselves in principle in practice. However, the manner in which the spinning yarn is overtaken by the rotating yarn catch device as well as the separating of the spinning yarn which is initially still running into the supply tube have proved to be disadvantageous. That is, both the undefined overtaking of the spinning yarn by the yarn catch device as well as the somewhat unreliable separating of the spinning yarn often result in relatively long yarn ends that are not fixed on the empty tube. These long, unsecured yarn ends have often proven to be problematic during the subsequent winding process since they frequently wind around component parts, which then results in a destruction of the start reserve winding. The relatively long yarn end can also get into or be wound under the bobbin winding preventing the yarn from subsequently being grasped when the yarn reserve is required. In addition, there is the danger that the yarn end can be removed by the suction of the suction nozzle and disposed of upon a yarn break, especially if the cheese still has a relatively small diameter.
In light of the above-discussed state of the art, it is accordingly an object of the present invention to provide a service unit whose yarn moving device makes possible an orderly, reliable and reproducible fixation of the spinning yarn on an empty tube held in the creel of a winding device.
The invention addresses this objective by providing a service unit for restarting a spinning operation in work stations of an open-end spinning machine after replacement of a yarn cheese with an empty cheese-winding tube. Basically, the spinning machine comprises multiple work stations, each work station having a spinning device for producing a yarn and a winding device for winding the yarn into a cheese, with each winding device comprising a creel having spaced tube plates for supporting the cheese-winding tube. The service unit comprises an auxiliary yarn supply device for providing an auxiliary yarn for restarting the spinning operation after a replacement of a yarn cheese with an empty cheese-winding tube and a yarn moving device for fixing a new spinning yarn on the empty cheese-winding tube held in the creel of the winding device. The service unit has a tube plate opener operative for creating a slotted opening between one of the tube plates of the winding device and an adjacent end of the cheese-winding tube. In accordance with the present invention, the yarn moving device is arranged for movement from a resting position entraining the auxiliary yarn held by the auxiliary yarn supply device into the area of the winding device and for positioning in the slotted opening the spinning yarn connected to the auxiliary yarn after restarting the spinning operation, the tube plate opener being arranged for subsequently closing the slotted opening to clamp the spinning yarn, the service unit having a yarn cutting device for separating the spinning yarn from the auxiliary yarn and a storage device for intermediately storing the spinning yarn.
Service units with a yarn moving device arranged and designed in accordance with the present invention have the particular advantage that they reliably assure that the new spinning yarn is always fixed in a secure and reproducible manner on the empty tube held in the creel and that the unsecured yarn end is relatively short. That is, the new spinning yarn connected after the spinning restart via a so-called spinning start yarn to the auxiliary yarn by the new yarn moving device can be positioned in such a manner in the area of the winding device and the creel can be loaded in such a manner that a yarn strand held in the creel extends between one of the tube plates of the somewhat open creel and between the adjacent front side of an empty tube held in the creel. The spinning yarn is clamped between the tube plate and the empty tube by a subsequent closing of the creel and thereby is immediately and reliably fixed. In addition, the spinning yarn is separated immediately behind the empty tube so that the free yarn end is always only relatively short. The spinning yarn that continues to run in during the clamping is intermediately stored thereby in a storage device.
In an advantageous embodiment, the yarn moving device comprises functional elements which can be shifted approximately axially to the axis of rotation of the empty tube and guide the new spinning yarn in such a manner onto the empty tube that it forms the desired yarn reserve winding thereat. That is, a yarn reserve winding is produced that reliably remains in its given position during the winding process as well as during subsequent transport procedures but is readily accessible and can be easily detached in case of need.
In a preferred embodiment, the yarn moving device also comprises a carrier arm that is supported in such a manner that it can pivot to a limited extent and can be axially shifted, on the end of which carrier arm are arranged functional elements that can be controlled in a defined manner. Both the carrier arm and the functional elements are designed to be relatively simple but robust and thus not very susceptible to problems.
Moreover, the yarn moving device is supported so that it can rotate to a limited extent and also shift axially, preferably relative to a pivot axis. That is, the radial and the axial movement of the yarn moving device take place via a separate defined drive for each that can be controlled in a defined manner. The drives are designed in an advantageous embodiment as thrust piston transmissions. Such thrust piston transmissions have the advantage that the end points of a movement can be reached at all times in a reproducible manner, especially without additional sensor devices or the like. In addition, such thrust piston transmissions are characterized by a long service life and excellent reliability.
Thus, the carrier arm can be pivoted by such a thrust piston transmission without problems and at any time in an exactly reproducible manner between a rear rest position and a front work position.
A corresponding thrust piston transmission in the area of the pivot axis makes possible an axial movement of the carrier arm, e.g., in order to open the creel. That is, the yarn moving device can be moved axially in such a manner by this thrust piston transmission that a tube plate opener arranged on a head element of the yarn moving device and resting on one of the tube plates of the creel of the winding device presses the tube plate outward. The tube plate involved is tilted in such a manner that a wedge-shaped slot is formed between the tube plate and a front surface of the empty tube held in the creel into which slot a portion of the auxiliary yarn or of the new spinning yarn can be placed.
The portion of the spinning yarn or of the auxiliary yarn extends in this instance between a deflection roller fixed on the yarn placing head and between a spring-loaded yarn guide device arranged on the head element.
The movement of the yarn strand into the wedge-shaped slot preferably takes place by a simple pivoting of a yarn placing head pivotably supported on the head element. That is, the yarn placing head is supported in such a manner that it can pivot in a limited fashion about a pivot shaft, and can be pivoted downwardly by a drive, e.g., a thrust piston transmission, in such a manner that a yarn portion is stretched between the front side of the empty tube and the tube plate.
Preferably, the yarn placing head comprises various functional elements, e.g., a yarn cutting device and a yarn brake. The yarn cutting device and the yarn brake can be actuated with preference by a common drive that is also fixed to the yarn placing head. A thrust piston transmission can also be provided as the drive.
Further details, features and advantages of the present invention will be described and understood from the following disclosure of an exemplary embodiment with reference to the accompanying drawings.